1. Field of the Invention
The embodiments described herein relate to biomedical telemetry devices, and more particularly to miniature wireless biomedical telemetry devices and methods of their use.
2. Background
The untethered monitoring of disease and injury in animal models, primarily in rats and mice, and comparable monitoring of humans in cases of suspected or demonstrated disease or injury, is important for the development of new therapies, determining markers for seizures or other acute events, and the development and application of treatment protocols.
Currently, monitoring physiological signals such as electroencephalogram (EEG), electrocardiogram (ECG), blood pressure, etc. requires cumbersome monitoring systems that generally involve surgical implantation and/or have limited monitoring time because of power consumption and, in humans, require expensive hospital stays with numerous electrodes, and as a minimum, result in limited mobility and otherwise prevent a normal way-of-life.
Epilepsy is the second most prevalent neurological disorder with over 50 million people affected worldwide. Nearly three million individuals in the U.S. have epilepsy, and over 30% are refractory to treatment with antiepileptic drugs (AEDs). The medical, psychological, sociological and financial implications of refractory epilepsy can be devastating for both the patient and their families. Seizures can be debilitating and result in major irreversible morbidity, often with long-term consequences that may include brain damage from recurrent seizures, seizure-induced injuries and accidents associated with loss of consciousness, impairment of memory, and even death. The personal consequences of refractory epilepsy may include the adverse effects of AEDs, strained personal and family relations, and the inability to obtain and hold meaningful employment or even a driver's license. Thus, there is a need for better approaches and new technologies for discovering novel therapies for intractable epilepsy.
One of the most widely used techniques for recording epileptic seizures is the EEG. This technique remains the mainstay to diagnose epilepsy, and to help localize the seizure onset zone in people with intractable epilepsy. As in the clinical diagnosis of the epilepsies, the EEG has become indispensable for translational research in animal models of both genetic and acquired epilepsy. This technique is also widely used to provide fundamental information about the mechanisms of sleep and to diagnose sleep disorders. For some research, “wired” or “tethered” recordings are quite acceptable and can be done in adult rats for weeks at a time. However, electrical noise, movement artifacts, and the risk that tethered animals will injure themselves by pulling on the cable have led to the need for radio-telemetry over the last several years. Current “wireless” systems, however, often involve extensive surgery to implant the transmitter and battery system, an expensive and time-intensive process. Other systems use a relatively large and awkward “back-pack” on the animal, which causes animal stress similar to a tether.
Further, acquired epilepsy (i.e., after brain injury, of many possible types) affects up to about 3 percent of the human population, and acute seizures after various forms of brain injury impact a much higher proportion. For example, post-traumatic epilepsy affects up to about 53 percent of adults suffering moderate to severe traumatic brain injury (TBI). Importantly, seizures early after TBI, similar to stroke, are associated with increased injury and poorer outcomes. Thus, optimal acute therapy for TBI victims and other individuals with brain injuries includes prompt seizure detection and effective therapy leading to seizure cessation. Continuous EEG monitoring reveals that roughly 25 percent of adults suffering moderate or severe TBI exhibit electrographic seizures, despite therapeutic levels of anticonvulsive medications. Nearly 60 percent of post-traumatic seizures in adults suffering severe TBI are non-convulsive seizures and can be detected only by EEG monitoring.
Aggressive, monitor-guided, early anti-seizure medical therapy may mitigate secondary brain injury after TBI and reduce the probability and severity of subsequent cognitive deficits or post-traumatic epilepsy. Ideally, EEG monitoring would be initiated as soon as possible after TBI, in order to detect non-convulsive seizures and guide anti-seizure therapy in the transport or pre-hospital setting. Reliable EEG recording during medical transport or field care will require a small device that can be properly positioned on the head quickly and lacks cumbersome cables or receivers. Unfortunately, an easy-to-use, telemetric, portable recording device is not currently available.
What are needed, therefore, are devices and methods of use that overcome challenges found in the current state of the art, some of which are described above.